| Paper |
Title |
Page |
| TUPLT024 |
A Comparison of High Current Ion Beam Matching from an Ion Source to a RFQ by Electrostatic and by Magnetic Lenses
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1192 |
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- R. Becker, R.A. Jameson, A. Schempp
IAP, Frankfurt-am-Main
- T. Hata, N. Hayashizaki, H. Kashiwagi, K. Yamamoto
RLNR, Tokyo
- T. Hattori, M. Okamura, A. Sakumi
RIKEN, Saitama
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In order to improve the ?direct? injection scheme of the Riken Nd-YAK-laser driven ion source into a RFQ rf-accelerator, several basic methods have been investigated and compared, in order to transform the initially divergent ion beam into a convergent one, needed for matching the high current (100 mA C6+) ion beam at an energy of 100 keV to a RFQ. From the point of power supplies and break down characteristics, the simplest solution is a decelerating electrostatic lens, with the decelerating electrode operated on ion source potential. Due to the strong divergence of the ions beam after acceleration, this lens will be filled to an aperture, which causes strong aberrations. Therefore, we also investigated to use an accelerating potential on the lens electrode. This reduces significantly the filling of the lens and the emittance growth is only a factor of 3, as compared to the decelerating lens with a factor of 30! Finally we have been looking also into a magnetic matching system, which can match the ion beam to the RFQ with virtually no emittance growth.
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| TUPLT025 |
Matching of a C6+ Ion Beam from a Laser Ion Source to a RFQ
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1195 |
| |
- R. Becker, R.A. Jameson, A. Schempp
IAP, Frankfurt-am-Main
- T. Hattori
RIKEN, Saitama
- N. Hayashizaki, H. Kashiwagi
RLNR, Tokyo
- M. Okamura
RIKEN/RARF/CC, Saitama
- K. Yamamoto
RIKEN/RARF/BPEL, Saitama
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A laser ion source, driven by a Nd-YAG laser can provide more than 100 mA of C6+ ions for a duration of about 1 μs, which is well matching the task of single-turn injection into synchrotrons for hadron tumor therapy with light ions. The ?direct? injection scheme has been improved by providing a design, which reduces the surface field strength to less than 30 kV/cm on all critical parts on relative negative potential. The new design keeps the advantage of divergent ion emission and acceleration, which seems to be the only way to keep the surface fields in limits, but includes a decelerating electrostatic lens on birth potential of the ions to refocus the emerging ion beam to the RFQ entrance. The whole design is very compact and allows for electrostatic steering between the ion source and the RFQ.
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